Using mask modes

Using mask modes, you can create complex mask shapes with multiple transparent areas. For example, you can set a mask mode that combines two masks and sets the opaque area to the areas where the two masks intersect.


Mask shapes that result when different modes are applied to circle mask A. Original masks B. None C. Add D. Subtract E. Intersect F. Lighten G. Darken H. Difference

To apply a mask mode:

1. In the Timeline window, select the layer containing the mask to which you want to apply a mode and press M.
2. Click the menu next to the mask name and choose a mask mode.

The following mask mode descriptions are based on interactions between two layer masks--the top set to Add, the other set to the mask mode described:

None

After Effects treats the mask as if it does not exist. The mask has no impact on the layer or composition. This option is useful when you want to use the mask's path for an effect such as Stroke or Fill, but do not want it to create transparent areas in the layer. (See Applying effects to a mask.)

Add

Adds the selected mask area to the other masks for that layer, displaying all mask contents in the Composition window. Where multiple masks intersect, the opacity of all intersecting masks is added together.

Subtract

Subtracts the mask from all masks located above it in the Timeline window. The contents of the subtracted mask area display as a hole in the Composition window. This option is useful when you want to create the appearance of a hole in the center of another mask.

Intersect

Adds the mask to all masks above it, but displays in the Composition window only the area where the selected mask and any of the previous masks intersect. Where multiple masks intersect, the opacity of all intersecting masks is added together.

Lighten

Adds the mask to all the masks above it, displaying contents of all masked areas in the Composition. Where multiple masks intersect, the highest opacity value is used, so opacity doesn't build up.

Darken

Adds the mask to all masks above it, but displays in the Composition window only the area where the selected mask and any of the others intersect. Where multiple masks intersect, the highest transparency value is used, so transparency doesn't build up.

Difference

Adds the selected mask to the masks above it, and displays in the Composition window the mask contents of all masked areas except those areas where the masks intersect.